transducers for side and down imaging?
I'm in the market for a new humminbird depth finder. Probably going to buy one of the 800 series units. Just wondering is there any drawbacks using the trolling motor transducer for the side and down imaging units. I'll be fishing the flowage in late oct and early November, I'm sure the bow of my boat is going to be beaten by the waves as I slip down the channels.
Thank you
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Sideimaging probably not the best idea...
I think a downimaging unit would be great on a trolling motor, but the main advantage would be for vertical fishing and being able to position more accurately over cribs, rock bars, weed edges, etc. because the edges would be defined more accurately than on a 2D unit (see attached sketch).
There are definitely some constraints to be aware of if you're thinking about mounting a sideimaging unit up front. For a good sideimaging picture, you need to be traveling in a fairly straight line at a steady speed - the screen is just a blur if you're standing still or turning. You're shooting a pair of narrow beams straight out to the sides, and when you turn you're essentially increasing the speed of the beam traveling over the bottom at an uneven rate - faster the farther it gets from the boat, and worse the faster/tighter the turn. An odd analogy, but it's kind of like making a snow angel - your fingertips cover a lot more distance than your upper arms in the same amount of time, and that's what's happening with the sideimaging beams when the transducer turns. It creates a motion blur that's worst at the edges of the screen. Again, see the attached sketch - I'll try to remember to make some demo screen shots next time I'm out and post them so you can see what it actually looks like on screen. Anyway, since you tend to be turning the boat a lot when you're running the trolling motor, it really limits the usefulness of having a sideimaging unit up front - particularly if the sideimaging transducer is mounted on the motor, because the motor turns a lot more than the boat itself - you might turn the motor 90 degrees to turn the boat 10 degrees.
Sideimaging works best as a surveying tool to help you scan an area using straight-line passes and either mentally visualize the structure to help you understand what you're casting to, or mark specific spots on GPS which you can then use for navigation or as virtual marker buoys for vertical fishing, and in general it's more efficient to do that from the console and not waste your battery doing it with the TM. You'll usually switch to a 2D view (conventional or downimaging) when you're actually fishing anyway. And putting a big, $234 transducer on the bottom of your trolling motor in the TFF is a risky idea. The catch-22 is that sometimes you'd really like to have those GPS points on your bow unit for fine positioning with the TM.
One idea would be to mount the main sideimaging transducer at the stern and a 2D puck on the trolling motor. With the accessory Y-cable, the unit will take depth and 2D data from the puck, and side- and down-imaging from the main transducer without the need for any manual switching. But then any GPS waypoints created in sideimaging view will be off by the length of the boat, which is fine as long as you're aware of that limitation. Still, I think that once you saw the things sideimaging does best, you'd find yourself wishing it was on the console so you could use it to cover larger areas using your big motor, unless of course you can afford to buy two and network them, eliminating most of the compromises...
For more information, Yahoo! has a great Humminbird users group with a discussion board, mounting photos and lots of screenshots. A couple factory guys chime in regularly to answer questions: http://groups.yahoo.com/group/sideimaging/